2 ACR LTTS MAY HAVE HAD A CONFLICT.

Narrative

AFTER DEPARTING LAX; WE CONTACTED SO CAL DEP. WE WERE ASKED IF WE HAD COMPANY IN SIGHT. WE DID. THE CTLR ADVISED US TO MAINTAIN VISUAL SEPARATION AND ADVISED COMPANY THAT A BRASILIA WOULD BE CLBING ABOVE THEM FROM THEIR 6 O'CLOCK POS. WE WERE CLRED TO 6000 FT MSL. I ADVISED THE FO; WHO WAS FLYING; THAT WE WOULD HAVE TO INCREASE OUR CLB RATE. HE COMPLIED. WHEN WE LEVELED OFF AT 6000 FT; OUR AIRSPD INCREASED RAPIDLY TO 230 KIAS. I HAD THE COMPANY ACFT IN SIGHT AT ABOUT 11 O'CLOCK LOW. WE WERE PROCEEDING TO VTU AS CLRED. THE FO CALLED FOR CRUISE PWR WHICH I SET. WHEN I LOOKED UP THE FO ASKED ME IF I STILL HAD THE ACFT IN SIGHT. I LOCATED THE ACFT JUST AS IT WAS ABOUT TO PASS UNDER THE NOSE. SINCE ITS POS LIGHTS WERE BACKGNDED BY THE BLACK OCEAN; I COULD NOT TELL EXACTLY HOW CLOSE WE CAME TO THE OTHER ACFT; BUT I THOUGHT WE HAD AT LEAST 1000 FT CLRNC. PERHAPS I HAD THOUGHT THIS BECAUSE OF THE ADVISORY THAT THE CTLR HAD MADE TO OUR TFC ABOUT US PASSING OVERHEAD; BUT I HAD NEVER VERIFIED WHAT ALT OUR TFC WAS CLBING TO. AFTER WE PASSED; THE CREW OF THE METROLINER CAME ON THE FREQ AND SAID 'NOT FUNNY GUYS.' I DID NOT KNOW THAT COMMENT WAS FOR US UNTIL THE CREW ASKED ATC FOR THE FLT NUMBER OF THE BRASILIA THAT JUST PASSED. I THEN ANSWERED WITH OUR FLT NUMBER AND SAID THAT I WAS ON COMPANY FREQ. I SPOKE TO THE CREW AND EXPLAINED THAT WE THOUGHT THEY WERE 1000 FT BELOW. I DID NOT KNOW HOW CLOSE WE HAD COME TO THE OTHER ACFT UNTIL THE FOLLOWING EVENING WHEN THE FO OF OUR ACFT SPOKE TO THE CAPT OF THE OTHER ACFT WHO SAID THAT WE PASSED WITHIN 200 FT OF THEIR ACFT. IF OUR ACFT HAD BEEN EQUIPPED WITH TCASII; THEN THE AURAL WARNING WOULD HAVE GOTTEN MY ATTN BACK OUTSIDE FROM SETTING CRUISE PWR QUICKLY. I ALSO SHOULD HAVE VERIFIED WITH THE CTLR WHAT ALT OUR TFC WAS CLBING TO. WE WERE BOTH ON IFR FLT PLANS IN VFR NIGHT CONDITIONS. IT WAS PITCH BLACK OUT THERE AND A COUPLE OF BLINKING RED LIGHTS ARE NOT THE BEST WAY TO JUDGE CLOSURE RATES. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTING ACFT WAS CLRED TO 6000 FT. BOTH RPTING PLTS BELIEVED THAT THE OTHER ACFT WAS CLRED ONLY TO 5000 FT; WHEN IN ACTUALITY IT WAS CLRED TO 9000 FT. THE RPTING CAPT WAS WATCHING THE OTHER ACFT ALL OF THE TIME AND DOES NOT BELIEVE THAT HER ACFT CAME 'THAT CLOSE' TO THE OTHER ACFT. THE FO OF THE OTHER ACFT MADE AN IRREGULARITY RPT TO HIS ACR COMPLAINING OF THE AIR TFC SIT. THE ACR HAS CONTACTED ZLA ABOUT THIS SIT. THE RPTING CAPT BELIEVES THAT ZLA AND LAX TWR ARE NOW MORE CAREFUL WHEN LAUNCHING A BRASILIA BEHIND A METROLINER BECAUSE OF THE DIFFERENCE IN PERFORMANCE; BOTH CLB AND CRUISE. SUPPLEMENTAL INFO FROM ACN 272831: RELATIVE SPD DIFFERENCE BTWN OUR ACFT (ESTIMATED 50-75 KTS). WE BOTH AGREED THERE WAS AT LEAST 1000 FT VERT AND SOME LATERAL SEPARATION. EVEN WITH LEGAL SEPARATION; WHEN WE PASSED THEM FROM BEHIND AND TO THE SIDE IT PROBABLY STARTLED THEM. WE HAD OUR LNDG LIGHTS; STROBES AND POS LIGHTS ON; SO WE PROBABLY APPEARED CLOSER THAN WE ACTUALLY WERE. SUPPLEMENTAL INFO FROM ACN 273595: WE WERE CLRED DIRECT VTU CLB TO 9000 FT. CLBING THROUGH 5500 FT; THE COPLT EXCLAIMED; 'WHAT THE HELL!' I LOOKED UP TO SEE A SAME ACR BRAZILIA PASS OVER THE TOP OF US AT NO MORE THAN 200 FT ABOVE US; SAME DIRECTION. WE ASKED THE CTLR FOR THE FLT NUMBER; THEY GAVE US X. EVIDENTLY; FLT X WAS BEHIND US AND REQUESTED TO MAINTAIN VISUAL SEPARATION WITH US SO THEY COULD PASS US. THEY LEVELED AT 6000 FT DIRECT VTU; WE WERE CLBING THROUGH 5500 FT FOR 9000 FT ALSO DIRECT VENTURA AND GOT DANGEROUSLY CLOSE TO US.